A very high percentage of the cruising public is above the age where the CV is especially contagious and lethal. These cruisers are insisting that cruise lines reopen with the objective of zero infections.
That will work against the younger cruisers, under 55, that the big cruise lines like CARNIVAL- ROYAL CARIBBEAN- NOREGIAN-MSC who need the younger people to be successful.
Hospital ship rules might be OK for a cruise line like VIKING, and a few others.
IMHO the many ships cruise lines are going to have to reduce their fleets, as cruising isn't going to be what it used to be. -Tom